ECG Data Acquisition Device

ABSTRACT

An apparatus for generating ECG recordings and a method for using the same are disclosed. The apparatus includes a handheld device and a controller. The handheld device has first, second, third, and fourth electrodes on an outer surface of the handheld device. The controller records signals from the first, second, third, and fourth electrodes and generates an ECG recording from the signals. The controller also provides placement information regarding locations on a user&#39;s body that are to be brought into contact with the first, second, third, and fourth electrodes while the controller records the signals. The handheld device can include a cellular telephone or a PDA. The controller stores an exemplary normal ECG recording, and compares a newly generated ECG recording with the stored ECG recording and generates an indication that indicates whether the newly generated ECG recording is consistent with the stored ECG recording.

BACKGROUND OF THE INVENTION

A number of systems that utilize remote ECG measurements to analyze acardiac patient's condition have been proposed. These systems includesome form of ECG electrodes that are attached to the patient's body andconnected to a local processor carried by the patient. The localprocessor typically includes a transmitter that relays the measurementsfrom the unit worn by the patient to a physician at a remote location.The relay mechanism can utilize a telephone line, either land orcellular, or some form of dedicated transmitter.

This system requires that electrodes be attached to the patient's body.To provide a full 12 lead ECG recording set, electrodes are typicallyattached to the patient's upper and lower limbs, as well as to a numberof locations on the torso. If the patient is in a setting in which thepatient has only limited mobility, such a set of attached electrodes maybe acceptable; however, if the patient is fully mobile and attending tohis or her normal routine outside of a medical environment, temporary orpermanent attachment of the electrodes is not usually acceptable andinvolves a fair amount of discomfort. Furthermore, the electrodes mustbe removed when the patient bathes. Hence, some arrangement in which thepatient or a care giver places the electrodes on the patient's body atthe time an ECG is to be recorded is needed.

A system based on the use of adhesively coated electrodes such as thoseutilized in normal ECG measurements presents problems from a logisticaland cost point of view. The individual electrodes are only usable for asmall number of measurements before the adhesive fails. Furthermore, therepeated placement and removal of the electrodes can cause patientdiscomfort, particularly in patients having body hair in the areas towhich the electrodes must be attached.

Systems that utilize electrodes that are held against the body ratherthan being adhesively attached have been proposed. For example, U.S.Pat. No. 7,112,175 discloses a “glove” having electrodes on thefingertips. If the glove is correctly positioned, a number of ECGmeasurements can be made; however, the device assumes a constantrelationship between the dimensions of the glove and the correspondingECG measurement points on the patient's body, since the electrodepositions are fixed relative to one another. In addition, not all of themeasurements provided by the conventional lead ECG tests are provided bythe glove.

Finally, the glove must be connected by cables to the transmitter thatreceives the data and either processes the data or transmits the data toa central processing system. While such arrangements are feasible in theconfines of a patient's home, this type of system becomes problematic ifthe patient is at work or traveling. In this regard, it should be notedthat a cardiac patient who is going about his or her normal life maydetect an irregularity at any time and wish to verify that he or she isnot suffering a cardiac event. The event can occur in any of a number ofsettings that do not lend themselves to providing a monitoring apparatusand leads for connecting the patient to the apparatus.

SUMMARY OF THE INVENTION

The present invention includes an apparatus for generating ECGrecordings and a method for using the same. The apparatus includes ahandheld device and a controller. The handheld device has first, second,third, and fourth electrodes on an outer surface of the handheld device.The controller records signals from the first, second, third, and fourthelectrodes and generates an ECG recording from the signals. Thecontroller also provides placement information regarding locations on auser's body that are to be brought into contact with the first, second,third, and fourth electrodes while the controller records the signals.The handheld device can include a cellular telephone or a PDA. In oneaspect of the invention, the apparatus also includes an adapter thatconnects 4 ECG leads to the apparatus, the controller utilizing the fourECG leads in combination with the fifth electrode to measure aconventional ECG recording.

In another aspect of the invention, the controller stores an exemplarybaseline ECG recording, and the controller compares a newly generatedECG recording with the stored ECG recording and generates an indicationif the newly generated ECG recording is consistent with the stored ECGrecording. The exemplary baseline ECG recording could be a previouslyrecorded ECG recording or a signal derived from a plurality ofpreviously recorded ECG recordings.

In another aspect of the invention, the apparatus includes acommunication device that sends and receives messages from an externalfacility. The controllers communicate the newly recorded ECG recordingto the external facility if the indication indicates that the newlygenerated ECG recording is inconsistent with the stored ECG recording.

In yet another aspect of the invention, the apparatus includes amicrophone and speaker. The controller communicates instructions to theuser via the speaker and receives communications from the user via themicrophone while the controller generates the ECG recording. Theapparatus could also include a buzzer and/or vibrator that causes theapparatus to vibrate when the vibrator is activated. The controlleractuates the buzzer and/or vibrator when the controller is generating anECG recording. The microphone can also be utilized to record heartsounds.

In another aspect of the invention, the apparatus includes a circuit fordetermining if the first, second, third, and fourth electrodes are incontact with the user's body.

The apparatus can be utilized to provide patient generated ECGrecordings that replicate the standard lead recordings and areapproximations to the conventional Precordial ECG recordings. In themethod of the present invention, the patient is provided with anapparatus as described above. The patient grips the handheld device suchthat the first and second electrodes are in contact with a first hand ofthe patient such that the first and second electrodes contact differentlocations on the first hand. Simultaneously the patient makes contactwith the third electrode on the patient's other hand. During themeasurement, the patient places the fourth electrode at a predeterminedpoint on the patient's body, the predetermined point depending on theparticular ECG recording being generated. The signals as a function oftime between the first electrode and each of the second, third, andfourth electrodes are measured and converted into the ECG recording.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of an ECG data acquisition deviceaccording to the present invention.

FIG. 2 illustrates another embodiment of an ECG data acquisition deviceaccording to the present invention.

FIG. 3 illustrates another embodiment of an ECG data acquisition deviceaccording to the present invention.

FIG. 4 illustrates another embodiment of an ECG data acquisition deviceaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention is based on the observation that a full ECG can bemeasured with a 4 terminal device if the measurements are made one at atime. Refer now to FIG. 1, which illustrates one embodiment of an ECGdata acquisition device according to the present invention. ECG dataacquisition device 20 may be viewed as comprising two components. Thefirst component is a handheld device 30 such as a cellular telephone orpersonal data assistant (PDA). The second component, referred to as theelectrode component, is a set of electrodes and a controller that areattached to the outside of hand held device 30. The electrodes are shownat 21-24, respectively, and are separated from one another electricallyby insulating the insulating regions shown at 25 a-25 d. In one aspectof the invention, one or more of the insulating regions include anelastic member that allows the electrode component to be reversiblyattached to the handheld device 30.

The functions provided by controller 26 and switch 36 will be discussedin more detail below. For the purposes of the present discussion, it issufficient to note that the electrodes are connected to a controller 26and that controller 26 communicates with the data processor in handhelddevice 30. In addition, controller 26 provides the electrical interfacefor the signals communicated by electrodes 21-24 and preprocesses thosesignals. Controller 26 is connected to handheld device 30 through one ofthe conventional signal connections that are typically included inhandheld devices. The connections may include direct electricalconnections via an existing port such as an USB port or wirelessconnections such as Bluetooth.

The manner in which ECG data acquisition device 20 is used to generate a12 lead ECG will now be explained in more detail. A conventional 12 leadECG involves the placement of 10 electrodes at designated places on thepatient's body. The signals from these 10 electrodes are then processedto generate 12 graphs of voltage as a function of time that are calledthe ECG chart or diagram. In the conventional ECG measurements, 4electrodes are attached to the patient's limbs, typically on the wristsand ankles. These electrodes are referred to as the standard leadelectrodes. The remaining 6 electrodes are attached to specific pointson the patient's chest. These electrodes are referred to as thePrecordial electrodes.

A 12 trace ECG diagram is obtained using ECG data acquisition device 20by holding the ECG data acquisition device with both hands and pressingelectrode 24 against the appropriate place on the patient's body. In oneembodiment, electrodes 21 and 22 are held in the right hand with thethumb on electrode 21 and the right index finger on electrode 22. Theleft index finger or any part of the left palm is held on electrode 23.It should be noted that electrode 22 can be touched with other fingersof the right hand besides the index finger. Electrode 21 can also betouched with other fingers or part of the right hand. The type ofmeasurement being performed can be communicated to controller 26 throughmode switch 36, which has a plurality of predetermined positions. Forthe standard lead measurements, mode switch 36 is set to a firstposition, and electrode 24 is placed against any point of the left legor the lower abdomen. For the Precordial measurements, mode switch 36 isset to a second position, and electrode 24 is placed sequentially ateach of the Precordial positions on the patient's chest.

As noted above, the four conventional electrodes are placed on the leftand right wrists and the left and right ankles. In the presentinvention, these measurements are provided by using the potential fromthe right index finger, i.e., electrode 22, in place of the potentialfrom the right wrist, the potential from the right thumb, i.e.,electrode 21 in place of the potential from the right ankle, thepotential from the left index finger, i.e., electrode 23, in place ofthe potential from the left wrist, and the potential from the left leg,i.e., electrode 24 in place of the potential from the left ankle.

Denote the potential from electrode 21 by Φ_(g), the potential fromelectrode 22 by Φ_(r), the potential from electrode 23 by Φ_(l), and thepotential from electrode 24 by Φ_(f). The first three standard leadtraces are given by

I=Φ₁−Φ_(r)

II=Φ _(f)−Φ_(r)

III=Φ _(f)−Φ_(l) =II−I

Three additional traces are generated by utilizing weighted sums anddifferences of the potentials, namely

aVR=Φ _(r)−(Φ_(l)+Φ_(f))/2=−(I+II)/2

aVL=Φ _(l)−(Φ_(r)+Φ_(f))/2=I−II/2

aVF=Φ _(f)−(Φ_(l)+Φ_(f))/2=I−I/2

In one embodiment of the present invention, controller 26 performs thevarious potential measurements and calculations to provide the sixtraces in question. However, embodiments in which the computations arecarried out by the processor in the hand-held device or at an externalfacility connected to the hand-held device can also be constructed.

The remaining 6 traces are the Precordial traces (V1 . . . V6). In theconventional Precordial measurements, each trace is generated by formingthe average of the potentials from the right and left wrists and theleft leg (this averaged potential is known as the Central-TerminalΦ_(CT)) and then measuring the difference between Φ_(CT) and apotential, Φ_(i), detected by an electrode at a corresponding point onthe patient's chest. A different predetermined point on the chest beingused for each of the 6 traces. Again, the right leg is used as theground reference for each of these potentials. NamelyVi=Φ_(i)−(Φ_(r)+Φ_(l)+Φ_(f))/3.

In the present invention, a novel approximation to the conventionalPrecordial traces is obtained by using the average of the potentialsrecorded from the left and right index fingers in place of Φ_(CT). Theaveraging function can be performed in hardware that is introduced intothe signal paths when the mode switch is set to the Precordial positionor by software in the controller or handheld device. This potential willbe denoted by Φ_(AT) in the following discussion. The approximationsutilized in the present invention for the Precordial traces are given by

R _(i)=Φ_(i)−Φ_(AT)=Φ_(i)−(Φ_(r)+Φ_(l))/2.

It can be shown that R_(i) is a good approximation of V_(i).

The potential from the right thumb is again utilized as the groundreference. For each measurement, the device is placed against theappropriate location on the chest such that electrode 24 is in contactwith the location in question. It should be noted that for these tests,electrode 24 may include a protrusion 31 surrounded by an insulatingarea that limits the area of contact so that only the desired locationis in contact with electrode 24.

As noted above, the R_(i) are approximations to the conventional V_(i)traces. In some cases, corrections to the Precordial signal measuredR_(i) to compensate for the missing leg potential Φ_(f) may bedesirable. If there are no significant changes between different Cardiaccycles of the aVF trace, the data recorded from the previous standardlead measurement of aVF can be utilized to correct the R_(i)measurements to obtain a better approximation of the V_(i) tracesaccording to the relationship:

V _(i) =R _(i) −aVF/3=Φ_(i)−(Φ_(r)+Φ_(l)+Φ_(f))/3

This method deviates from the conventional measurement in that thesignals are not recorded simultaneously. When the ECG signals changesignificantly in time, the approximation to V_(i) may actually be lessaccurate than the R_(i). Such changes occur during an arrhythmia. Thismode of operation for the Precordial leads measurements requires thatstandard leads be measured a short predetermined time before or afterthe Precordial measurements to assure that a valid aVF signal isobtained when performing the aVF correction. If the person for somereason did not measure the standard leads, the device detects it andnotifies via an alarm so that the person can perform the standard leadsmeasurements.

In one embodiment of the present invention, the Precordial traces aremeasured one at a time. However, embodiments in which a plurality ofmeasurements is made simultaneously can also be constructed. Refer nowto FIG. 2, which illustrates another embodiment of an ECG dataacquisition device according to the present invention. ECG dataacquisition device 40 is similar to ECG data acquisition device 20discussed above with reference to FIG. 1 in that it includes a hand helddevice that receives data from a plurality of electrodes via acontroller 46 which can include a mode switch such as switch 36discussed above or utilize other input devices for indicating the modeof operation. In ECG data acquisition device 40, electrode 24 of ECGdata acquisition device 20 has been replaced by a Precordial electrodestructure having a plurality of electrodes that are spaced such thateach electrode makes contact with a different Precordial location whenECG data acquisition device 40 is properly placed on the patient'schest. In the embodiment shown in FIG. 2, the Precordial electrodestructure includes two fixed electrodes shown at 41 and 42 and amoveable member 44 that pivots within the Precordial electrode structureto provide additional electrodes such as electrode 43 when member 44 isdeployed from its storage position within the Precordial electrodestructure. When the standard lead traces are being generated moveablemember 44 is stored within the Precordial electrode structure andelectrodes 41 and 42 are pressed against the patient's leg. During thestandard lead measurements, electrodes 41 and 42 are connected togetherto form a single electrode.

As noted above, the traces obtained by using the present invention areapproximations to those obtained with a conventional ECG system in thecase of the Precordial measurements. For many purposes, the differencesbetween the conventional and approximation traces are insignificant inthat the purpose of the test is to detect a change in the patient'scondition. For example, the portable ECG apparatus of the presentinvention can be used by the patient to determine that symptomsexperienced by the patient are the result of a cardiac problem asopposed to some other problem. In this situation, a comparison of theECG traces during the symptomatic period with those previously measuredwith the same device when the patient was not symptomatic can besufficient to determine if a potential cardiac problem has arisen. Insuch an application, the handheld device stores the previously measuredtraces (or has access to these traces by a network connection) andcompares those traces to the newly measured traces during thesymptomatic period to determine if a significant change has occurred inthe traces. If the new traces differ from the stored traces by more thana predetermined manner, the patient's results can be transferred via thehandheld device to the medical facility responsible for the patient'scare and the patient notified that a problem exists. If the traces arenot significantly different from the stored trace, the patient can benotified of that result by the handheld device and the patient can thencontinue with his or her normal activities. In addition, in many cases acomparison to previously taken traces is not needed, and a diagnosis canbe done solely based on the current traces.

To carry out such a comparison, the handheld device needs to store oneor more sets of traces taken with the present invention and informationconcerning the expected variability of the traces from measurement tomeasurement during non-symptomatic periods. Traces taken during thenon-symptomatic periods will be referred to as baseline approximationtraces in the following discussion. A number of such baselineapproximation trace sets can be generated by the patient in the doctor'soffice during a training period in which the patient is taught to usethe present invention by a nurse. The handheld device can then generatean average baseline approximation trace set and a measure of thestatistical variability of the traces in the set. This average normalapproximation trace set can then be used in the field as the comparisontrace set with which new approximation trace sets are compared todetermine if the patient's heart has undergone a significant change.

In one aspect of the present invention, each time the patient acquires anew set of traces with the present invention, the new set is stored inthe handheld device or the controller. Periodically, these stored tracesare readout and transmitted to the medical facility that is responsiblefor the patient's care. These traces can then be analyzed in a moredetailed manner to provide data on the functioning of the patient'sheart over an extended period of time during normal activities. Thesetraces can also be analyzed statistically to provide a new averagenormal approximation trace set for use in comparing new traces generatedby the patient.

In another aspect of the present invention, each time the patientrecords a new set of traces with the handheld device, the patient alsoenters textual material on his hand held device describing theconditions that caused the patient to make the measurement, thepatient's activity level, etc. This information is stored with thetraces and readout when the recorded traces are readout. The textualinformation can be useful in analyzing the recorded measurements. Forexample, a comparison of all of the traces taken after the patient hasexercised can be analyzed together to provide information on the mannerin which the patient's heart is responding to such stresses.

In some cases, the differences between the approximation traces and theconventional traces may be important. In another aspect of the presentinvention, the controller also includes a socket for connecting 4conventional test electrodes. Refer now to FIG. 3, which illustratesanother embodiment of an ECG data acquisition device according to thepresent invention. ECG data acquisition device 60 is similar to ECG dataacquisition device 20 discussed above, and hence, those elements of ECGdata acquisition device 60 that perform functions that are analogous tofunctions performed by elements of ECG data acquisition device 20 havebeen given the same numerical definitions and will not be discussed indetail here. In ECG data acquisition device 60, controller 66 includes aport 62 that accepts a plug 75 that includes 4 conventional ECG leads71-74. When plug 75 is inserted into port 62, controller 66 disconnectsand replaces the signals from electrodes 21-23 with signals derived fromleads 71-74 and generates the conventional Central-Terminal signalΦ_(CT) for use in performing the Precordial measurements.

During the recording of data utilizing the conventional electrodes, theconventional electrodes are attached to the patient in the same manneras the standard electrodes are connected during a conventional ECGmeasurement, i.e., on the patient's ankles and wrists. The standard leadmeasurements are made in the conventional manner using only these 4electrodes. During the Precordial trace measurements, the device isplaced in the Precordial mode by utilizing mode switch 36 or other inputcommand to the controller. Electrode 24 is placed at each of thePrecordial points on the patient's chest and a conventional ECG trace isgenerated utilizing the signals from 4 standard leads connected to port62 and the signal from electrode 24.

Hence, when the 4 standard electrodes are connected to ECG dataacquisition device 60 a set of conventional ECG traces can be generatedby using the signals from these electrodes and electrode 24. Thesetraces can be used for two purposes. First, if the approximation tracesindicate that the patient's condition has changed significantly, thepatient's doctor may wish to immediately measure a conventional set ofECG traces to provide a more detailed diagnosis of the patient'scondition as close in time as possible to the event that caused thepatient to record the approximation traces. In this situation, thepatient, or a third party, can place the conventional leads on thepatient's wrists and ankles so that the patient, or the third party, canrecord the conventional traces for transmission to the doctor using thehandheld device, since any signals from electrodes 21-23 are ignored bythe controller when plug 75 has been inserted into port 62, the thirdparty can safely hold the device without having his or her own ECGsignals interfering with the measurements.

The standard electrode leads must have several feet of wire to connectthe electrodes to the ECG data acquisition device. These leads present astorage problem when not in use. In one embodiment of the presentinvention, the standard lead electrodes are stored in a rigid sleevethat also provides the connection to the ECG data acquisition device.Refer now to FIG. 4, which illustrates an embodiment of the presentinvention that utilizes a sleeve as the connector to the ECG dataacquisition device. ECG data acquisition device 80 operates in a manneranalogous that described above with respect to ECG data acquisitiondevice 60. When the standard lead electrodes are connected to ECG dataacquisition device 80, controller 86 operates in a manner to provide theconventional ECG measurements as described above. The standard leadelectrodes 81-84 are connected to a sleeve 90 that can also be used tostore the electrodes when the electrodes are not connected to ECG dataacquisition device 80. Sleeve 90 includes 4 contact members that makeelectrical contact with pads on the outer surface of ECG dataacquisition device 80 when sleeve 90 is slipped over ECG dataacquisition device 80. Each contact member includes a spring-loadedcontact. An exemplary contact member 91 is shown in contact with amating contact pad 88 in the drawing. In one aspect of the invention,the mating contact pads are disposed on the outer surface of theelectrodes that are gripped by the user during the normal operation(i.e., the non-standard lead mode) of the invention. In this case, oneof the outer electrodes is divided into two electrically isolatedportions as shown at 85 and 87. One of the contacts can include a switchor other sensor that detects the connection of sleeve 90 and causescontroller 86 to alter its functioning accordingly.

In one aspect of the invention, the handheld device stores theconventional traces recorded by ECG data acquisition device 60 duringnon-symptomatic periods with the newly recorded traces to determine ifthe difference in the conventional traces is also significant. Thesetraces can be used to calibrate the approximation traces. By comparingthe traces obtained with the conventional electrodes with theapproximation traces, the differences can be determined, and in somecases, corrected. For example, a linear model that relates each standardtrace to a linear combination of the approximation traces can begenerated by determining the weighting coefficients applied to each ofthe approximation traces that provides the best fit to the data measuredwith both types of electrodes.

The controller of the present invention can utilize the data entrymechanism and display of the handheld device to reduce the circuitryneeded to implement the controller. Many handheld devices include akeyboard or an emulated keyboard on a touch screen. In addition, manyhandheld devices include a port for connecting the handheld device to acomputer so that the handheld device can synchronize certain files onthe handheld device with corresponding files on the computer. The portcan be a wireless connection such as Bluetooth or WiFi or a wiredconnection such as a USB port. By altering the code in the handhelddevice, the controller of the present invention can takeover theprocessor in the handheld device during ECG measurements andtransmissions. Hence, the handheld device can provide the interface tothe medical facility either through the Internet or the local wirelesstelephone network.

The above-described embodiments of the present invention utilize anelectrode system and controller that is attached to an existing handhelddevice such as a cellular telephone or handheld computer PDA. However,embodiments in which the present invention is built into a handhelddevice and the electrodes are part of the case of that device can alsobe constructed. For example, an existing PDA or cellular telephone couldbe reprogrammed to perform the signal acquisition and computationfunctions of the controllers discussed above. The case of the existingPDA or cellular phone would be replaced by a case having the electrodesdescribed above. For the purposes of this discussion, a handheld deviceis defined to be any computing device that is held in the user's handand that can be positioned on the user's body to make the measurementsdescribed above.

The above-described embodiments require that the controller be able todetect the presence of the user and determine that the user is holdingthe device in an acceptable manner to provide sufficient electricalconnections between the user and the present invention. In addition, thedevice must be able to signal the user when a measurement begins andends, so that the user knows when to proceed to the next measurementpoint. In one embodiment of the present invention, electrodes 21-24include pressure sensors that detect the force that the user is applyingto the device. For example, electrodes 21-24 can include strain gaugesthat measure the force applied to the electrodes. In another embodiment,the controller measures the capacitance or resistance between thevarious electrodes. When the user is holding the device with therequired pressure, the capacitance of the user's body alters thecapacitance measured between the ground electrode and each of theelectrodes in question. Similarly, the user's body presents a finiteresistance between each pair of electrodes that can be measured. In oneaspect of the invention, the controller activates an alarm to notify thepatient that the controller detected that the patient's hands or legsare touching each other or another part of the patient's body to preventsuch contact from interfering with the measurements.

Finally, the controller can look for a missing signal on any of theelectrodes and notify the user that the device is positionedincorrectly. If the controller does not detect a minimum number ofcardiac cycles, the controller can notify the user to continue to holdthe device or to repeat the recording.

During a series of measurements, the present invention communicates withthe user at a number of points in the measurement process for eachmeasurement. First, the present invention must communicate thepositioning of the invention with respect to the user's body for thecurrent measurement. Once the device is positioned properly, the usermust communicate this fact to the present invention so that the presentinvention can initiate the desired measurement. At this point, thepresent invention verifies that the user is holding the presentinvention in the prescribed manner by using one of the measurementsdiscussed above. If the measurements are consistent with the presentinvention being properly positioned, the present invention initiates thecurrent measurement. If not, the present invention signals the user tocorrect the problem.

The present invention also preferably generates a signal that lets theuser know that a trace is being recorded so that the user does not movethe present invention before the trace is finished. When the measurementis finished, the present invention must signal the user that themeasurement has been completed and provide the setup directions to theuser for the next measurement.

In embodiments that include the speaker, display, and microphonecomponents of a cellular telephone or PDA, these components can beutilized in the communication process. For example, the positioning ofthe present invention relative to the patient's body can be displayedgraphically on the display. Similarly, the user can communicate with thepresent invention using the microphone to provide voice commands thatare interpreted by the processor in the cellular phone or PDA. In thisregard, it should be noted that voice activated call initiation is acommon feature in modern cell phones. Similarly, the present inventioncan communicate with the user via the speaker. It should also be notedthat many cellular telephones have a vibrate mode that can also beutilized for communication. For example, when a measurement is beingmade, the present invention can vibrate. When the vibration terminates,the user knows that the measurement is finished.

Refer again to FIG. 3. In one embodiment of the present invention,controller 66 includes a number of indicator lights 76, a buzzer, and/oracoustical transmitter 77 that can also be used to communicate statusand events to the user. In addition, controller 66 could also includehardware to implement one or more of the communication mechanismsdescribed above with respect to embodiments that include cellulartelephone functionality.

In the above-described embodiments of the present invention, thecontroller uses the microphone in the handheld device to receivecommands from the user. However, that microphone or another microphonethat is disposed on the outer surface of electrode 24 and is connectedto the controller can also be used to listen to the sounds of the heartin the Precordial recording mode. The acoustical signal can be comparedto the electrical signals to verify that the electrical signals arevalid.

The order in which the user grips the electrodes can also be utilized tosignal that the user is ready for the instrument to begin recording thenext trace. For example, the device is normally programmed such that theuser grips electrodes 21 and 22 with the right hand. Electrode 24 isthen placed at the appropriate point on the user's body. When the useris ready to begin the next trace, the user places his left index fingeron electrode 23. When controller 24 detects the user's finger onelectrode 23, controller 24 begins recording the next trace and signalsthe user by activating a busy signal such as a buzzer, vibrator, oraudio signal. When controller 24 completes the measurement, the busysignal is turned off.

The above discussion has assumed that the user is right handed. However,the present invention can be utilized by left handed individuals bysuitably programming controller 24 at the time the present invention issetup for a particular user. In this case, the device is gripped in theleft hand such that the thumb and index finger of the left hand are onelectrodes 21 and 22 and the device is activated by the user placing theuser's right index finger on electrode 23.

The above-described embodiments of the present invention utilize ahandheld device such as a cellular telephone or PDA as part of thepresent invention. In such embodiments, the native functions andcomputing power of the handheld device can be used to augment thecontroller. For example, the telephone can be utilized as a modem tocommunicate the results of the ECG measurements to a physician ormedical facility. In addition, in locations that include wirelessnetwork access, the cellular telephone or PDA can be used to connect tothat network. However, embodiments in which the handheld device ismerely a body that provides support for the electrodes and includes thecontroller discussed above can also be constructed. In this case, thebody could include limited functionality such as a wireless transmitterfor connecting the device to another device that provides thecommunication functions. For example, the handheld device or thecontroller could include a Bluetooth or other wireless transmitter thatallows the controller to communicate with a wireless access point or aconventional cellular telephone or PDA that provides the connection tothe physician or medical facility.

Various modifications to the present invention will become apparent tothose skilled in the art from the foregoing description and accompanyingdrawings. Accordingly, the present invention is to be limited solely bythe scope of the following claims.

1. An apparatus comprising: a handheld device having first, second,third, and fourth electrodes on an outer surface of said handhelddevice; a controller that records signals from said first, second,third, and fourth electrodes and generates an ECG recording from saidsignals; wherein said controller provides placement informationregarding locations on a user's body that are to be brought into contactwith said first, second, third, and fourth electrodes while saidcontroller records said signals,
 2. The apparatus of claim 1 whereinsaid handheld device comprises a cellular telephone or a PDA.
 3. Theapparatus of claim 1 further comprising an adapter that connects 4 ECGleads to said apparatus, said controller utilizing said four ECG leadsin combination with said fourth electrode to measure a conventional ECGrecording.
 4. The apparatus of claim 3 wherein said controllerdisconnects said first, second, and third electrodes when said 4 ECGleads are connected to said adapter.
 5. The apparatus of claim 1 whereinsaid controller stores an exemplary normal ECG recording and whereinsaid controller compares a newly generated ECG recording with saidstored ECG recording and generates an indication that indicates whethersaid newly generated ECG recording is consistent with said stored ECGrecording.
 6. The apparatus of claim 5 wherein said exemplary normal ECGrecording comprises a previously recorded ECG recording.
 7. Theapparatus of claim 5 wherein said exemplary normal ECG recordingcomprises an average of a plurality of previously recorded ECGrecordings.
 8. The apparatus of claim 5 wherein said apparatus furthercomprises a communication device that sends and receives messages froman external facility and wherein said controller communicates said newlyrecorded ECG recording to said external facility if said indicationindicates that said newly generated ECG recording is inconsistent withsaid stored ECG recording.
 9. The apparatus of claim 1 furthercomprising a microphone and speaker, wherein said controllercommunicates instructions to said user via said speaker and receivescommunications from said user via said microphone while said controllergenerates said ECG recording.
 10. The apparatus of claim 1 furthercomprising a mode switch operable by a user of said apparatus tocommunicate which of a plurality of measurements are to be made next.11. The apparatus of claim 1 further comprising a vibrator that causessaid apparatus to vibrate when said vibrator is activated and whereinsaid controller actuates said vibrator when said controller isgenerating an ECG recording.
 12. The apparatus of claim 1 furthercomprising a circuit for determining if said first, second, third, andfourth electrodes are in contact with said user's body.
 13. Theapparatus of claim 12 wherein said circuit comprises a pressure sensorassociated with one of said electrodes, said pressure sensor measuring aforce associated with said user gripping said apparatus at thatelectrode.
 14. The apparatus of claim 12 wherein said circuit comprisesan impedance measuring circuit that measures an impedance between pairsof said first, second, third, and fourth electrodes.
 15. A method forgenerating an ECG recording of a patient comprising: providing ahandheld device having first, second, third, and fourth electrodes on anouter surface of said handheld device; causing said patient to grip saidhandheld device such that said first and second electrodes are incontact with a first hand of said patient such that said first andsecond electrodes contact different locations on said first hand;simultaneously causing said patient to contact said third electrode witha predetermined location on said patient's other hand; simultaneouslycausing said patient to contact said fourth electrode at a predeterminedpoint on said patient's body, said predetermined point depending on saidECG recording; measuring signals as a function of time between saidfirst electrode and each of said second, third, and fourth electrodes;and converting said measured signals to said ECG recording.
 16. Themethod of claim 15 wherein said first and second electrodes are incontact with the thumb and finger on said patient's first hand.
 17. Themethod of claim 15 wherein said third electrode is contact with a fingeron said patients other hand.
 18. The method of claim 15 wherein saidfourth electrode is in contact with a predetermined point on one of saidpatient's legs.
 19. The method of claim 15 wherein said fourth electrodeis in contact with a Precordial measurement point on said patient'schest.
 20. The method of claim 15 further comprising comparing saidgenerated recording with an ECG recording stored in said handheld deviceand generating an indication that is receivable by said patient, saidindication indicating whether said generated ECG recording is consistentwith said stored ECG recording.
 21. The method of claim 20 furthercomprising communicating said generated ECG recording to a locationremote from said handheld device if said indication indicates that saidgenerated ECG recording is not consistent with said stored ECGrecording.
 22. A method for measuring Precordial ECG signals from apatient, said method comprising: placing a first electrode in contactwith one of said patient's hands; simultaneously placing a secondelectrode in contact with the other of said patient's hands;simultaneously placing a third electrode in contact with a Precordialpoint on said patient's chest; averaging signals from said first andsecond electrodes to provide an averaged signal; and measuring apotential difference between said averaged signal and a signal from saidthird electrode.
 23. The method of claim 22 wherein said potentialdifference between said averaged signal and said signal from said thirdelectrode is correct by subtracting a signal derived from a standardleads measurement made previously on said patient.